Count letter differences of two strings

Question

This is the behaviour I want:

a: IGADKYFHARGNYDAA
c: KGADKYFHARGNYEAA
2 difference(s).

Answer 1

When looping through one string, make a counter object that identifies the letter you are on at each iteration. Then use this counter as an index to refer to the other sequence.

a = 'IGADKYFHARGNYDAA'
b = 'KGADKYFHARGNYEAA'

counter = 0
differences = 0
for i in a:
    if i != b[counter]:
        differences += 1
    counter += 1

Here, each time we come across a letter in sequence a that differs from the letter at the same position in sequence b, we add 1 to 'differences'. We then add 1 to the counter before we move onto the next letter.